Vitamin D: The Sunshine Vitamin's Dark Side
The "sunshine vitamin" has been hailed as a health panacea, but new research reveals a hidden danger lurking in its rays. While a deficiency can lead to serious health issues, an excess of vitamin D can also be toxic, causing a range of unpleasant and potentially life-threatening symptoms.
For years, scientists have warned that not everyone needs vitamin D supplements, and that high-dose versions can be toxic, especially for young kids and older adults. As the supplement's popularity grows, so do the risks. The vast majority of people recover from vitamin D toxicity after discontinuing the supplements and receiving IV fluids or medication to lower calcium levels. However, in rare cases, if left untreated, vitamin D toxicity can lead to kidney failure requiring hemodialysis or even fatal intestinal bleeding.
One study suggests that older adults with high levels of vitamin D in the blood may be more at risk of falls. This raises a deeper question: How much is too much?
A 2018 review warned of "considerable complacency" regarding vitamin D's potential for toxic effects. Scientists still can't agree on exactly how much vitamin D is too much. This is perhaps not surprising, given the dramatic expansion in vitamin D interest, partly fueled by popular books extolling the virtues of high-dose vitamin D.
Vitamin D is produced by the body when exposed to sunlight, providing roughly 90% of the vitamin D an individual requires. The rest comes from foods containing the vitamin, such as fatty fish or fortified dairy. While vitamin D helps the body absorb calcium and maintain immune function, cell growth, metabolism, and neuromuscular activity, a lack of vitamin D for an extended period can raise the risk of neurological conditions, autoimmune conditions, bone disorders, and cardiovascular disease.
However, the effectiveness of vitamin D supplements remains controversial. While some studies suggest that these supplements can slow aging, boost cognition, or ease depressive symptoms, other scientists have cast doubt on their effectiveness. Plus, these supplements are not without their risks, often due to mistakes in treating vitamin D deficiency.
One notable case involved an 80-year-old man who was accidentally taking a weekly high-dose vitamin D tablet, prescribed by his naturopathic practitioner, each and every day. Thankfully, his hypercalcemia resolved once the mistake was recognized and the supplement was discontinued.
The problem is not limited to older adults. In 2016, the national health authority in Denmark issued a recall for a supplement containing 75 times the recommended level of vitamin D. Roughly 20 children experienced toxic effects because of the capsules. The same problem is becoming more common in the US, with over 25,000 cases of vitamin D toxicity reported from 2000 to 2014, and a 1600% increase from 2005 to 2011.
So, what's the solution? Doctors at Harvard advise that if someone has a vitamin D deficiency, they start with foods fortified with the vitamin, as these are much less likely to cause toxicity. They also recommend avoiding taking more than 15-20 mcg (600-800 IU) per day, unless medically recommended, and never exceeding 100 mcg (4,000 IU) per day.
In conclusion, while vitamin D is essential for good health, it's crucial to be aware of the potential risks associated with excessive intake. As always, when starting or ceasing any medication or supplement, it's best to consult a medical professional.
